Electronegativity Flashcards
What is electronegativity?
Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons.
What happens if two atoms of equal electronegativity bond together?
“pure” covalent bond - the electrons are shared evenly between the two atoms.
What is a polar bond?
a covalent bond in which there is a separation of charge between one end and the other - one end is slightly positive and the other slightly negative.
What happens if one atom is a lot more electronegative than the other?
Ions form. Less electronegative atom loses electrons and more electronegative atom gains electrons. Ionic attraction bonds the atoms
What happens if atom B is slightly more electronegative than atom A?
B end of the bond has more electron density and so becomes slightly negative. The A end (electron deficient) becomes slightly positive.
Why is CHCl3 a polar molecule?
The hydrogen at the top of the molecule is less electronegative than carbon and so is slightly positive.
Why is CCl4 not a polar molecule?
Symmetrical tetrahedral molecule so the effect of four polar bonds cancel out so no overall separation of charge.
What is the trend in electronegativity across a period?
As you go across a period the electronegativity increases (except argon) because the number of charges on the nucleus increases. This attracts the bonding pair of electrons more strongly.
What is the trend in electronegativity down a group?
As you go down a group, electronegativity decreases because the bonding pair of electrons is increasingly distant from the attraction of the nucleus.
There is an increase in the amount of screening by inner electrons.
Why is fluorine more electronegative than carbon?
the distance of the pair from both nuclei would be the same, as is shielding.
net pull of about 4+ from the carbon, but about 7+ from the fluorine. The extra nuclear charge pulls the bonding electron pair closer to the fluorine than the carbon.
Why isn’t chlorine as electronegative as fluorine?
net pull from either halogen nuclei of 7+, chlorine bonding pair is further away in third shell, so it feels the pull from the nucleus less strongly.
